#!/bin/sh

# Make sure there's backlight control
ls /sys/class/backlight/* >/dev/null 2>&1 || exit

process() {
    while read line; do 
        case "$line" in
            UNBLANK*)
                echo 0 | sudo tee /sys/class/backlight/*/bl_power 1>/dev/null
            ;;
            BLANK*)
                echo 1 | sudo tee /sys/class/backlight/*/bl_power 1>/dev/null
            ;;
        esac
    done
}

xscreensaver-command -watch | process